/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkNeighborhood_h
#define itkNeighborhood_h

#include <iostream>
#include "itkNeighborhoodAllocator.h"
#include "itkIndent.h"
#include "itkSliceIterator.h"
#include "vnl/vnl_vector.h"
#include "itkOffset.h"
#include <vector>

namespace itk
{
/** \class Neighborhood
 * \brief A light-weight container object for storing an N-dimensional
 * neighborhood of values.
 *
 * This class serves as the base class for several other Itk objects such as
 * itk::NeighborhoodOperator and itk::NeighborhoodIterator.  Its purpose is to
 * store values and their relative spatial locations.
 *
 * A Neighborhood has an N-dimensional \em radius.  The radius is defined
 * separately for each dimension as the number of pixels that the neighborhood
 * extends outward from the center pixel.  For example, a 2D Neighborhood
 * object with a radius of 2x3 has sides of length 5x7.  Neighborhood objects
 * always have an unambiguous center because their side lengths are always odd.
 *
 * \sa Neighborhood
 * \sa NeighborhoodIterator
 *
 * \ingroup Operators
 * \ingroup ImageIterators
 * \ingroup ITKCommon
 */

template <typename TPixel, unsigned int VDimension = 2, typename TAllocator = NeighborhoodAllocator<TPixel>>
class ITK_TEMPLATE_EXPORT Neighborhood
{
public:
  /** Standard class type aliases. */
  using Self = Neighborhood;

  /** External support for allocator type. */
  using AllocatorType = TAllocator;

  /** External support for dimensionality. */
  static constexpr unsigned int NeighborhoodDimension = VDimension;

  /** \see LightObject::GetNameOfClass() */
  itkVirtualGetNameOfClassMacro(Neighborhood);

  /** External support for pixel type. */
  using PixelType = TPixel;

  /** Iterator type alias support Note the naming is intentional, i.e.,
   * AllocatorType::iterator and AllocatorType::const_iterator, because the
   * allocator may be a vnl object or other type, which uses this form. */
  using Iterator = typename AllocatorType::iterator;
  using ConstIterator = typename AllocatorType::const_iterator;

  /** Size and value type alias support */
  using SizeType = itk::Size<VDimension>;
  using SizeValueType = typename SizeType::SizeValueType;

  /** Radius type alias support */
  using RadiusType = itk::Size<VDimension>;

  /** Offset type used to reference neighbor locations */
  using OffsetType = Offset<VDimension>;

  /** External slice iterator type alias support */
  using SliceIteratorType = SliceIterator<TPixel, Self>;

  /** Type used to refer to space dimensions */
  using DimensionValueType = unsigned int;

  /** Type used to refer to the elements of the pixel list
   * that are part of the neighborhood. */
  using NeighborIndexType = SizeValueType;

  /** Default constructor. */
  Neighborhood() = default;

  /** Default destructor. */
  virtual ~Neighborhood() = default;

  /** Copy constructor. */
  Neighborhood(const Self &) = default;

  /** Move-constructor. */
  Neighborhood(Self &&) = default;

  /** Assignment operator. */
  Self &
  operator=(const Self &) = default;

  /** Move-assignment. */
  Self &
  operator=(Self &&) = default;

  /** Comparison operator. */
  bool
  operator==(const Self & other) const
  {
    return (m_Radius == other.m_Radius && m_Size == other.m_Size && m_DataBuffer == other.m_DataBuffer);
  }

  ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(Self);

  /** Returns the radius of the neighborhood. */
  [[nodiscard]] const SizeType
  GetRadius() const
  {
    return m_Radius;
  }

  /** Returns the radius of the neighborhood along a specified
   * dimension. */
  [[nodiscard]] SizeValueType
  GetRadius(DimensionValueType n) const
  {
    return m_Radius.at(n);
  }

  /** Returns the size (total length) of the neighborhood along
   * a specified dimension. */
  [[nodiscard]] SizeValueType
  GetSize(DimensionValueType n) const
  {
    return m_Size.at(n);
  }

  /** Returns the size (total length of sides) of the neighborhood. */
  [[nodiscard]] SizeType
  GetSize() const
  {
    return m_Size;
  }

  /** Returns the stride length for the specified dimension. Stride
   * length is the number of pixels between adjacent pixels along the
   * given dimension. */
  [[nodiscard]] OffsetValueType
  GetStride(DimensionValueType axis) const
  {
    return (axis < VDimension) ? m_StrideTable[axis] : 0;
  }

  /** STL-style iterator support. */
  /** @ITKStartGrouping */
  Iterator
  End()
  {
    return m_DataBuffer.end();
  }
  Iterator
  Begin()
  {
    return m_DataBuffer.begin();
  }
  [[nodiscard]] ConstIterator
  End() const
  {
    return m_DataBuffer.end();
  }
  [[nodiscard]] ConstIterator
  Begin() const
  {
    return m_DataBuffer.begin();
  }
  /** @ITKEndGrouping */

  /** More STL-style support. */
  [[nodiscard]] NeighborIndexType
  Size() const
  {
    return m_DataBuffer.size();
  }

  /** Pass-through data access methods to the buffer. */
  /** @ITKStartGrouping */
  TPixel &
  operator[](NeighborIndexType i)
  {
    return m_DataBuffer[i];
  }
  const TPixel &
  operator[](NeighborIndexType i) const
  {
    return m_DataBuffer[i];
  }
  TPixel &
  GetElement(NeighborIndexType i)
  {
    return m_DataBuffer[i];
  }
  /** @ITKEndGrouping */

  /** Returns the element at the center of the neighborhood. */
  [[nodiscard]] TPixel
  GetCenterValue() const
  {
    return (this->operator[]((this->Size()) >> 1));
  }

  /** Sets the radius for the neighborhood, calculates size from the
   * radius, and allocates storage. */
  void
  SetRadius(const SizeType &);

  /** Sets the radius for the neighborhood. Overloaded to support an unsigned
   * long array. */
  void
  SetRadius(const SizeValueType * rad)
  {
    SizeType s;
    std::copy_n(rad, VDimension, s.m_InternalArray);
    this->SetRadius(s);
  }

  /** Overloads SetRadius to allow a single long integer argument
   * that is used as the radius of all the dimensions of the
   * Neighborhood (resulting in a "square" neighborhood). */
  void
  SetRadius(const SizeValueType);

  /** Standard itk object method. */
  void
  Print(std::ostream & os) const
  {
    this->PrintSelf(os, Indent(0));
  }

  /** Returns a reference to the data buffer structure. */
  /** @ITKStartGrouping */
  AllocatorType &
  GetBufferReference()
  {
    return m_DataBuffer;
  }
  [[nodiscard]] const AllocatorType &
  GetBufferReference() const
  {
    return m_DataBuffer;
  }
  /** @ITKEndGrouping */

  /** Get pixel value by offset */
  /** @ITKStartGrouping */
  TPixel &
  operator[](const OffsetType & o)
  {
    return this->operator[](this->GetNeighborhoodIndex(o));
  }
  const TPixel &
  operator[](const OffsetType & o) const
  {
    return this->operator[](this->GetNeighborhoodIndex(o));
  }
  /** @ITKEndGrouping */

  /** Returns the itk::Offset from the center of the Neighborhood to
      the requested neighbor index. */
  [[nodiscard]] OffsetType
  GetOffset(NeighborIndexType i) const
  {
    return m_OffsetTable[i];
  }

  [[nodiscard]] virtual NeighborIndexType
  GetNeighborhoodIndex(const OffsetType &) const;

  [[nodiscard]] NeighborIndexType
  GetCenterNeighborhoodIndex() const
  {
    return static_cast<NeighborIndexType>(this->Size() / 2);
  }

  [[nodiscard]] std::slice
  GetSlice(unsigned int) const;

protected:
  /** Sets the length along each dimension. */
  void
  SetSize()
  {
    for (DimensionValueType i = 0; i < VDimension; ++i)
    {
      m_Size[i] = m_Radius[i] * 2 + 1;
    }
  }

  /** Allocates the neighborhood's memory buffer. */
  virtual void
  Allocate(NeighborIndexType i)
  {
    m_DataBuffer.set_size(i);
  }

  /** Standard itk object method. */
  virtual void
  PrintSelf(std::ostream &, Indent) const;

  /** Computes the entries for the stride table */
  virtual void
  ComputeNeighborhoodStrideTable();

  /** Fills entries into the offset lookup table. Called once on
      initialization. */
  virtual void
  ComputeNeighborhoodOffsetTable();

private:
  /** Number of neighbors to include (symmetrically) along each axis.
   * A neighborhood will always have odd-length axes (m_Radius[n]*2+1). */
  SizeType m_Radius{ { 0 } };

  /** Actual length of each dimension, calculated from m_Radius.
   * A neighborhood will always have odd-length axes (m_Radius[n]*2+1). */
  SizeType m_Size{ { 0 } };

  /** The buffer in which data is stored. */
  AllocatorType m_DataBuffer{};

  /** A lookup table for keeping track of stride lengths in a neighborhood
      i.e. the memory offsets between pixels along each dimensional axis */
  OffsetValueType m_StrideTable[VDimension]{ 0 };

  /** */
  std::vector<OffsetType> m_OffsetTable{};
};

template <typename TPixel, unsigned int VDimension, typename TContainer>
std::ostream &
operator<<(std::ostream & os, const Neighborhood<TPixel, VDimension, TContainer> & neighborhood)
{
  os << "Neighborhood: " << std::endl;
  os << "    Radius: " << neighborhood.GetRadius() << std::endl;
  os << "    Size: " << neighborhood.GetSize() << std::endl;
  os << "    DataBuffer: " << neighborhood.GetBufferReference() << std::endl;

  return os;
}
} // namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkNeighborhood.hxx"
#endif

#endif
